Such pump stators are known from the state of the art and described, for example, in document DE 10 2005 028 818 B3. The stator disclosed in this document comprises a stator body made of a casing in the form of a smooth-cylindrical tube of steel and a lining of rubber or a rubber-like synthetic material. The casing of the stator body encompasses the lining and the lining tightly adheres to an inner wall of the casing of the stator body. An inner side of the lining defines an axially continuous cavity.
Document DE 10 2006 021 897 A1 discloses a stator casing having an elastic lining, wherein the stator casing comprises longitudinal grooves on the inside. The ends of the stator casing have a positive-fit connection with a closure strip in order to protect the stator casing from expanding in the pumping mode.
Furthermore, document DE 10 2010 000 923 A1 discloses a stator for an eccentric screw pump whose stator body is formed of a hollow cylindrical casing made of metal and an elastomer core which is firmly bonded to an inner casing surface of the hollow-cylindrical casing by means of vulcanization.
The state of the art also describes stators comprising a helical stator body. Such a stator is disclosed, for example, in document DE 198 04 259 A1. The stator according to this document essentially consists of a rigid casing being made of steel and a lining being made of rubber or a rubber-like synthetic material and being encompassed by the casing. The lining is connected to the casing in a tightly adhering manner, i.e., it contacts the inner side of the casing. The lining has a continuous cavity for accommodating a rotor. The inside and the outside of the casing have the contour and shape of the cavity and accordingly are likewise helical.
The stators known from the state of the art are mostly manufactured according to the scheme disclosed in DE 10 2010 000 923 A1.
According to this document, the stators known from the state of the art are manufactured in that first of all the casing of the stator body is cut to length in the required dimensions from a metal tube or steel tube. Subsequently, the casing of the stator body is chemically and/or mechanically cleaned roughly and thereafter finely as well as roughened in order to enhance the adherence between the casing and the lining made of rubber or a rubber-like synthetic material. Furthermore, the casing must be (chemically) pretreated at the connection site with the rubber such that a connection with the rubber can be effected. For the purpose of producing the helical or spiral hole, a preheated, helical core is inserted into the casing prepared for the firm bonding. Subsequently, the front ends of the casing are closed with lids and a caoutchouc mixture is injected. A connection between the casing and the rubber lining for forming the stator body is effected by a vulcanization of the rubber lining.
This type of production of a pump stator is very time-consuming and cost-intensive, i.a., because of the treatment and pre-treatment of the metal tube.
An object to be achieved with the present invention is the provision of a stator for a feed pump, in particular for an eccentric screw pump, which can be produced in a simple and cost-efficient way.
This object is achieved with a stator for a feed pump of the initially mentioned type in which the stator body is configured as an elastomer body reinforced at least in sections with a thread inlay.
By means of the stator body in the form of an elastomer body reinforced at least in sections with a thread inlay, it is possible to completely do without a metal tube or a firm and non-detachable bonding with a metal tube in the production of the stator for a feed pump. Thus, when producing the stator or rather the stator body for a feed pump, it is thereby possible to save in particular the expenses necessary for procuring and conditioning the metal tube and for its pre-treatment as well as to save the time involved in this connection, i.e. with the stator of the invention it is possible to reduce the production costs to a considerable extent.
Furthermore, the stator body according to the invention can be completely recycled since, in contrast to the usual practice in the state of the art, no non-detachable bonding with metal parts is effected.
When the stator according to the invention is used in a feed pump, such as, for example, an eccentric screw pump, higher torques than with the stators known from the state of the art can be accepted by the stator body constituted by an elastomer body reinforced with a thread inlay. During the operation of a feed pump and in particular during the operation of an eccentric screw pump, the helical rotor extending through the hole in the stator gets into contact with the elastomer core of the stator. Since the rubber lining according to the state of the art is vulcanized onto the tube made of metal, the connection site between the rubber lining and the metal tube represents a weak point of the stators known from the state of the art. When the torque exerted onto the rubber lining is too high, the rubber lining of the state of the art may be severed from the metal tube at the connection site with the metal tube.
This weak point is completely eliminated with the stator according to the invention. In the case of the stator according to the invention, there is no connection site between the rubber and a metal tube since the stator body is made completely and exclusively of an elastomer body into at least sections of which a thread inlay is embedded. In other words, the stator body of the stator according to the invention can move in the radial and also the axial direction since there is no connection to a metal tube. This freedom of motion achieved according to the invention entails that the service life can be extended and downtimes as well as wear as a whole can be reduced.